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通过从一个导数值等式的证明谈起,探讨教师在课堂教学中如何根据教学内容创设能激起学生新异感的问题情景,启发和引导学生发散思考,类比、联想、猜想,探索和发现新问题并给出解答.使学生思维不断攀升,丰富教学内容,激发学生兴趣,培养学生科学思维方法和创新能力. 相似文献
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We present a numerical investigation for steady laminar flow of a viscous incompressible electrically conducting fluid through a channel of a rectangular cross-section with a transverse magnetic field and suction or injection wails. Multiple solutions are presented for values of suction Reynolds number R and velocity coefficients of accelerating walls. Additionally, the associated transfer characteristics are discussed in detail. 相似文献
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分析了壁面具有不同渗透的涨缩管道内微极性流体的流动.对于壁面的胀缩,考虑常系数和时间函数的膨胀率两种情况.对于第1种情况,应用同伦分析方法得到该问题的速度和微旋转角度的表达式.并且画图分析了各个不同参数,特别是膨胀系数和不同的渗透率对流体的动力特征的影响.可以得到第1个重要的结论:壁面的膨胀率和不同的渗透对流体的动力特征有重要的影响.根据Xu的模型,考虑了第2种也是更具有一般性的情况,假设壁面的膨胀率随时间的变化而变化.在这样的假设下,控制方程被转化成非线性偏微分方程,并且同样也可以应用HAM方法进行求解.应用代数和指数的模型来描述膨胀率从初始状态到最终状态的演变过程.然而,结果表明包含有时间的解很快地趋向于稳态的解.这样可以得到第2个重要的结论,时间在壁面的膨胀收缩中扮演着次要的角色,可以忽略不计. 相似文献
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The unsteady,laminar,incompressible,and two-dimensional flow of a micropolar fluid between two orthogonally moving porous coaxial disks is considered.The extension of von Karman’s similarity transformations is used to reduce the governing partial differential equations(PDEs) to a set of non-linear coupled ordinary differential equations(ODEs) in the dimensionless form.The analytical solutions are obtained by employing the homotopy analysis method(HAM).The effects of various physical parameters such as the expansion ratio and the permeability Reynolds number on the velocity fields are discussed in detail. 相似文献
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An unsteady magnetohydrodynamic (MHD) boundary layer flow over a shrinking permeable sheet embedded in a moving viscous electrically conducting fluid is investigated both analytically and numerically. The velocity slip at the solid surface is taken into account in the boundary conditions. A novel analytical method named DTMBF is proposed and used to get the approximate analytical solutions to the nonlinear governing equation along with the boundary conditions at infinity. All analytical results are compared with those obtained by a numerical method. The comparison shows good agreement, which validates the accuracy of the DTM-BF method. Moreover, the existence ranges of the dual solutions and the unique solution for various parameters are obtained. The effects of the velocity slip parameter, the unsteadiness parameter, the magnetic parameter, the suction/injection parameter, and the velocity ratio parameter on the skin friction, the unique velocity, and the dual velocity profiles are explored, respectively. 相似文献
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We present a theoretical analysis for heat transfer in power law non-Newtonian fluid by assuming that the thermal diffusivity is a function of temperature gradient. The laminar boundary layer energy equation is considered as an example to illustrate the application. It is shown that the boundary layer energy equation subject to the corresponding boundary conditions can be transformed to a boundary value problem of a nonlinear ordinary differential equation when similarity variables are introduced. Numerical solutions of the similarity energy equation are presented. 相似文献
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MHD Boundary Layer Flow of a Non-Newtonian Fluid on a Moving Surface with a Power-Law Velocity 下载免费PDF全文
A theoretical analysis for MHD boundary layer flow on a moving surface with the power-law velocity is presented. An accurate expression of the skin friction coefficient is derived. The analytical approximate solution is obtained by means of Adomian decomposition methods. The reliability and efficiency of the approximate solutions are verified by numerical ones in the literature. 相似文献